1. Field of the Invention
This invention relates to a scale testing vehicle, and more particularly to a vehicle for use in section testing and calibration of the vehicle scale.
2. Description of the Prior Art
Truck weighing stations need to be tested periodically to ensure their accuracy. Such stations include those along highways maintained by state highway departments to determine compliance with vehicular weight restrictions and those weigh stations at industrial plants which are used to determine the weight of truck deliveries.
Most states require that the scales alongside highways be calibrated at periodic intervals. These scales are calibrated by placing a known weight on the scales and comparing the reading obtained with the correct weight. On large scale platforms, commonly as long as 110 feet, the scale must be calibrated not only by placing a known weight on the platform but also by placing that weight on various sections of the platform. The standard section length used for such calibration is 10 feet. Such testing ensures that the scale provides the proper reading no matter how the weight is situated on the platform.
One testing method which has been used is to deposit blocks of a known weight on the scale. However, 20,000 lbs. is commonly deposited on the scales in this manner and it is difficult and very time consuming to move these weights from section to section on a single scale platform as is often required. Further, greatest scale errors have been found in the higher weight categories on large scale platforms so that test weights over 20,000 lbs. are preferred, state highway officials and the like having found it desirable to calibrate the scale with a known weight on the order of 40,000 lbs. Unfortunately, depositing that many weight blocks on each section would double the time currently required to calibrate the scale with 20,000 lbs.
Another method which has been used for section testing of large scale platforms is to provide a remotely controlled weight cart, that cart having a known weight and being small enough to apply the load to only a 10 foot section. However, such a cart must be transported between stations in a truck, taking up considerable space in the truck and limiting the amount of calibrated weights which may be transported. Further, such carts have been able to hold only a limited weight which is far less than the desired 40,000 lbs.
Still another device which has been used is disclosed in Dunbar U.S. Pat. No. 4,048,843, issued Sept. 20, 1977. In that patent, a truck is disclosed which can transport calibrated weights and which has hydraulic lifting legs for raising the front wheels of the truck so that the entire weight is supported by the rear wheels and the lifting legs. With this truck, a large weight may be relatively quickly applied to a 10 foot section for testing the scale. However, this weight must be applied at stopped positions and accordingly, the scale may not be tested over an infinite number of sections. Further, the lifting legs must be retracted and then re-extended each time that the truck is moved to a different section, showing the speed at which such testing may be done.
The present invention is directed to overcoming one or more of the problems as set forth above.